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SH4DY

EFI V8 ITB balancing and link bars

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Posted (edited)

So I've got the OBX (Jenvey knock off) ITB's for my LS6 based motor and I'm trying to sort out a better way to tie the throttle bodies together. I can take pictures later but right now, the throttle shafts are tied together by a little arm on the first TB that presses up on a set screw on the next throttle body to open the blade. Then the second presses on the 3rd and so on. Then, there is a (flimsy) piece that sits on the top side so when the first TB closes it'll coax the second one to close as well if the spring tension isn't enough. 

I get that the set crew is there to balance the throttle bodies BUT I have drilled and tapped every runner (about 2" off the head as that was the only place with enough meat to tap) and have 5/16" vacuum line tying them all together at a distribution block. I did this for a couple of reasons: one, I didn't want to run only Alpha-N so I needed a MAP reference and two, I thought it would help balance the runners. (And maybe my logic is jacked here but if you have a high vacuum and introduce a lower vacuum ( a leak essentially) then the higher vacuum can only pull as much as the lower). And if this holds true, then I wouldn't need to sync each throttle independently and I could have a rigid linkage between the throttles for a crisper response instead of the daisy chain approach. 

 

Thoughts?

Edited by SH4DY

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Alright, now that I have the car running:

You absolutely need to have each throttle body adjustable. It will run like absolute dog sh*t unless they are synced, per bank and bank to bank. And the adjustments are very small, like 1/4 turn on an M4 bolt. I also went through the painstaking process of drilling and tapping every single runner and then tied them into a vacuum manifold to get a good MAP sensor reading. No Alpha-N needed, it tracks on the VE just like a normal manifold does but you need to ramp up the tps accel enrichment because it revs very, very quickly. 

Getting the crossover linkage sorted out was also a massive pain in the ass. 

 

If I did it again I might flip the TB's 90* and use an adjustable heim joint or something like this:

https://www.jegs.com/i/JEGS/555/15795/10002/-1?gclid=EAIaIQobChMIx9e22LT55AIVFIrICh0mgAz7EAQYBSABEgKwhfD_BwE

 

But, for the minimal amount of driving I'll realistically be doing, the current set up should be fine for now. 

20190703_221303.jpg

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